In general this invention relates to fuel management systems for internal combustion engines and in particular to systems utilizing exhaust gas sensors for controlling and maintaining any desired fuel/air ratio in a fuel injection system.
B. Prior Art
In U.S. Pat. No. 3,815,561 issued to Seitz and entitled "Closed Loop Engine Control System" the system described therein is responsive to signals indicative of the presence or absence of oxygen in the exhaust gas of the engine. The control system is then operative to generate an output signal for receipt by the fuel delivery controller which will cause that controller to increase fuel delivery in the presence of oxygen molecules and to decrease fuel delivery in the absence of oxygen molecules. Thus, in response to the output signal the controller attempts to maintain fuel delivery at a predetermined and in particular stoichiometric air/fuel ratio mixture point.
U.S. Pat. No. 3,789,816 issued to Taplin et al, and entitled "Lean Limit Internal Engine Roughness Control System" describes a closed loop fuel control mechanism for controlling the air/fuel mixture delivered to an internal combustion engine. The purpose of this system is to regulate the roughness of the engine at a predetermined level by controlling the fuel delivery mechanism so that the engine is operated at the leanest possible air/fuel mixture ratio compatible with a predetermined level of engine roughness.
Most systems teach the use of a single sensor which is responsive to one predetermined air/fuel ratio in order to maintain the system at that air/fuel ratio. As indicated above when such sensor is an oxygen gas sensor of a particular type it generates a step voltage signal at a particular air/fuel ratio which is stoichiometric. Functionally the output of the sensor is supplied to an integrator circuit having an output that is symmetrical as respects to charge and discharge times thereby allowing the fuel controller to operate equally on both sides of the stoichiometric point.